1. Field of the invention
This invention relates to a suspended work platform testing apparatus and a method of load testing a work platform suspended from a crane.
2. Discussion of the Technical Problems
Work platforms known as manbaskets are small platforms or stages within which workmen can be transported vertically to worksites. Generally, such manbaskets are suspended from cranes or derricks and are hoisted by the crane or derrick to position workers at the worksite.
Although cranes are material handling devices, manbaskets are used extensively due to their low cost, flexability, speed, and convenience. Such use raises safety issues and invites regulations regarding suspended manbaskets.
Cranes have different boom lengths and extensions so that for any given setup having a set boom length and angle of boom placement, only a certain amount of weight can be carried in the manbasket.
In order to ensure that the operation of the crane is safe, a proof load test and trial lift is required by the Occupational Safety and Health Administration (OSHA). OSHA also mandates a manufacturing requirement that the platform must be designed to support five times the maximum intended load (including the workers as well as associated light tools). In addition, separate load tests must be used whenever repairs are made to the platform. Effective Oct. 3, 1988, OSHA has amended its standards for cranes and derricks as found in 29 C.F.R. 1926.550 by prohibiting the use of cranes or derricks to hoist personnel except in the situation where no safe alternative is possible and as long as a number of requirements are met. These requirements include that a trial lift with the unoccupied personnel platform loaded at least to the anticipated lift weight shall be made from ground level or any other location where employees will enter the platform to each location at which the personnel platform is to be hoisted in position. This trial lift shall be performed immediately prior to placing personnel on the platform. A single trial lift may be performed at one time for all locations that are to reached from a single setup position. Additionally, at each job site prior to hoisting any employees on the personnel platform and after any repair modification, the platform and rigging shall be proof tested to 125 percent of the platform's rated capacity by holding it in a suspended position for five minutes with the test load evenly distributed on the platform. Such nondestructive field testing provides the necessary assurance that any defect in the platform or rigging would be detected and corrected before any personnel were hoisted.
The OSHA requirements thus include both a proof test to test the capacity and construction of the personnel platform and also a trial lift to determine that the lifted route is free of obstacles, to determine work location accessibility, to confirm that no work locations will place the crane or derrick in such a configeration where the intended load would exceed the 50 percent limit of the crane's rated capacity, to ensure soil or other supporting surface stability and to determine suitability for the intended lift. The proof test and trial lift can be conducted simultaneously.
In order to provide the testing as required by OSHA, it has been found that sandbags, metal weights, and other objects with known weight can be employed by placing them in the manbasket. Unfortunately, the movement of hundreds and thousands pounds of material on and off the manbasket is difficult, time consuming, and in itself a dangerous activity. The constant testing mandated by OSHA which is intended to provide safety for the workers would be greatly enhanced if there existed a convenient apparatus for attaching test weights to the manbasket. Such a device should employ weight of a known value and should be attached to the manbasket in a secure manner to evenly distribute the weight and yet be quickly released or attached as needed.
Since a crane easily lifts the manbasket vertically, it would be most convenient if the manbasket were made so it could be placed over a known weight. The weight could then be securely attached to the manbasket and both the proof testing as well as the trial lift could be conducted.
No known examples of manbasket testing devices have been discovered. Very few devices in the known art relate to testing of cranes, cables, and the like and none known are directed to providing a manbasket testing apparatus and method.
Accordingly, a need exists for a manbasket testing apparatus that would provide a safe, convenient work platform while in use and yet the testing device could be easily detached for testing to comply with government safety regulations. Such a device should be easily repaired, not subject to damage by proper use, and simple to manufacture. The instant invention is directed to all these needs as well as to others as explained in the following summary.